Fat representation is not as trendy as lbgtq+ and racial representation and at the end of the day is all about money. Does the cost of adding fat bodies to the game will make enough profit? If not, there's no point for them to add it. It is what it is.
It doesn't affect me in any way whether they add it or not but as I always say, having the option is always better. I also don't understand the need some people seem to have to self insert into the game, I've been playing almost 30 years and I've played characters of any gender,race,sexual orientation and species under the sun and I've had fun regardless... But again, having options is ALWAYS better.